The disclosure relates to ion exchangeable glasses. More particularly, the disclosure relates to ion exchangeable glasses that, when ion exchanged has a surface layer that is under a compressive stress of at least about 1 GPa.
The ion exchange process is used to strengthen glass by creating a compressive stress at the glass surface by replacing of relatively large alkali ions such as K+ from a salt bath with smaller alkali ions such as Na+ in the glass. Since glasses typically fail under tension, the created compressive stress at the surface improves the glass strength. Ion exchanged glasses thus find use in various applications such as touch-screen devices, hand held electronic devices such as communication and entertainment devices, architectural and automotive components, and the like.
When strengthened by ion exchange, a glass should simultaneously be provided with high compressive stress at the surface and a deep depth of the ion exchange layer. Soda-lime glasses are difficult to chemically strengthen by ion exchange as they require long salt bath treatment times to achieve reasonable strength by ion exchange.